1. Field of the Invention
The present invention relates to an ink delivery system of delivering ink used for development in a liquid-type electrophotographic printer, and an ink delivery method thereof.
2. Description of the Related Art
In general, a liquid-type electrophotographic printer is an apparatus in which an electrostatic latent image is formed on a photosensitive medium by scanning the photosensitive medium with a plurality of laser beams, thereafter, the electrostatic latent image is developed with ink and the developed image is transferred onto a paper sheet. The ink used in development is a mixture of a powder toner and a liquid solvent.
FIG. 1 shows a portion of a liquid type electrophotographic printer. As shown in FIG. 1, a liquid type electrophotographic printer includes developing units 20 for developing respective electrostatic latent images with ink having predetermined colors to form a visible image, a drying unit 30 for drying the developed image to an extent appropriate for transferring the developed image onto a paper sheet at a transfer unit (not shown), and an ink delivery system 40 for supplying ink having a concentration and a quantity which are appropriate for development to the developing units 20, and for resupplying the solvent recovered by the drying unit 30 to circulation tanks 45. FIG. 1 shows a conventional liquid-type electrophotographic, color printer. In FIG. 1, only a developing unit corresponding to a black developer is shown, and other developing units corresponding to yellow (Y), magenta (M), and cyan (C) developers are omitted.
Ink used in development is made by mixing concentrated ink supplied from ink tanks 41 and a liquid solvent supplied from a solvent cartridge 44 or a condensing tank 39 connected to the drying unit 30 in a predetermined ratio to dilute the concentrated ink.
The ink delivery system 40 includes ink tanks 41 for storing concentrated ink, a solvent tank 42 for storing a solvent, concentrated ink refill cartridges 43 of pressurized-can-type refill cartridges for refilling the respective ink tanks 41 with respective new supplies of concentrated ink when the concentrated ink in the ink tanks 41 is consumed, a solvent refill cartridge 44 of a pressurized-can-type refill cartridge for refilling the solvent tank 42 with a new supply of a solvent when the solvent in the solvent tank 42 is consumed, circulation tanks 45 for storing appropriately mixed mixtures of ink supplied from the ink tanks 41 and the solvent supplied from the solvent tank 42, supply portions 47 for supplying the ink in the circulation tanks 45 to the developing units 20 and a waste ink tank 49 for temporarily storing ink drained from the circulation tanks 45 through respective waste ink recovery passages 48.
The circulation tanks 45 are installed below the respective developing units 20 and they supply ink to the respective developing units 20. The circulation tanks 45 also circulate, receive and resupply the ink which does not take part in development. Concentration sensors 46 are installed at the respective circulation tanks 45 for sensing respective concentrations of developers contained in the circulation tanks 45.
The ink tanks 41 and the solvent tank 42 store concentrated ink and a solvent supplied from the pressurized-can-type ink cartridges 43 and solvent cartridge 44 which can discharge the contained liquid with pressurized air as described above, and supply the concentrated ink and the solvent to the circulation tanks 45 in predetermined ratios. When any one of the corresponding concentration sensors 46 detects that the concentration of the ink in a corresponding one of the circulation tanks 45 is out of a predetermined range, the corresponding ink tank 41 and the solvent tank 42 supply the concentrated ink and the solvent to the corresponding circulation tank 45 in a controlled manner so that the concentration of the ink in the corresponding circulation tank 45 can be within the desired range. Reference numerals 41a and 42a denote level sensors for detecting remaining quantities of the ink and the solvent stored in the ink tanks 41 and the solvent tank 42, respectively. When the level sensors 41a and 42a detect that the ink and the solvent in the tanks 41 and 42 are consumed, the consumed tanks 41 and 42 are refilled with new supplies of the ink and the solvent from the ink cartridges 43 and the solvent cartridge 44.
However, in the above-described ink delivery system, since the concentrated ink and the solvent contained in the ink cartridges 43 and the solvent cartridge 44 are first transferred to the ink tanks 41 and the solvent tank 42 provided with the level sensors 41a and 42a, respectively, and then supplied to the circulation tanks 45 in order to control ink and solvent supplies and refills in the system, it""s disadvantageous that the number of containers installed in a printer is large.
In addition, the above level sensors 41a and 42a usually employ a level measuring method in which ink levels are measured by detecting varying capacitances of the ink. As a matter of course, there are other level sensors, employing a floater, or an ultrasonic wave, besides the level sensor employing the capacitance measuring method. However, those level sensors are not employed in this application. A floater may malfunction if it adheres to an inner wall of a container, and a level sensor using an ultrasonic wave is very expensive and is too large for this application. Also, in the above capacitance measuring method, the level sensor may respond to ink adhering to the inner wall of a container, and detect an ink level erroneously. Therefore, in order to enhance the operational stability of an ink delivery system, it is desirable that the number of such level sensors is reduced as much as possible.
Consequently, if exhaustion of ink filled in a container can be known without a level sensor, the number of parts can be reduced, possibility of erroneous operations of level sensors can be reduced, and, in addition, the number of containers in an ink delivery system can be reduced since concentrated ink and a solvent need not be transferred to containers having level sensors. Therefore, new types of ink delivery system and ink delivery method are required for realizing the above.
To solve the above problem, it is an objective of the present invention to provide an ink delivery system and an ink delivery method of a liquid-type electrophotographic printer which are adapted to detect whether or not liquid in any one of containers which supply ink and a solvent to circulation tanks is exhausted without installing separate level sensors.
Accordingly, to achieve the above objective, there is provided an ink delivery method of a liquid-type electrophotographic printer for supplying concentrated ink and a solvent to circulation tanks receiving ink to be supplied to respective developing units including the steps of: (a) preparing ink cartridges which store concentrated ink to be supplied to the circulation tanks; (b) preparing a solvent cartridge which stores a solvent to be supplied to the circulation tanks; (c) detecting an ink concentration of each circulation tank using predetermined concentration sensors which correspond to respective circulation tanks; (d) adjusting the ink concentration of any one of the circulation tanks by supplying the concentrated ink from a corresponding one of the ink cartridges to a corresponding one of the circulation tanks when the ink concentration of the corresponding circulation tank is lower than a predetermined range; (e) generating a message, even after a preset number of the ink concentration adjusting steps are repeated, signaling that the concentrated ink in the corresponding ink cartridge is consumed when the ink concentration is not within the predetermined range; (f) adjusting the ink concentration of any one of the circulation tanks by supplying the solvent from the solvent cartridge to a corresponding one of the circulation tanks when the ink concentration of the corresponding circulation tank is higher than a predetermined range; and (g) generating a message, even after a preset number of the ink concentration adjusting steps are repeated, signaling that the solvent in the solvent cartridge is consumed when the concentration is not within the predetermined range.
According to another aspect of the present invention, there is provided an ink delivery method of a liquid-type electrophotographic printer for supplying concentrated ink and a solvent to circulation tanks receiving ink to be supplied to respective developing units including the steps of: (a) preparing ink cartridges which store concentrated ink to be supplied to the circulation tanks; (b) preparing a solvent cartridge which stores a solvent to be supplied to the circulation tanks, (c) providing a level sensor for detecting a quantity of the solvent remaining in the solvent cartridge; (d) detecting an ink concentration of each circulation tank by using predetermined concentration sensors which correspond to respective circulation tanks; (e) adjusting the ink concentration of any one of the circulation tanks by supplying the concentrated ink from a corresponding one of the ink cartridges to a corresponding one of the circulation tanks when the ink concentration of the corresponding circulation tank is lower than a predetermined range; (f) generating a message, even after a preset number of the ink concentration adjusting steps are repeated, signaling that the concentrated ink in the corresponding ink cartridge is consumed when the concentration is not within the predetermined range; (g) using a corresponding level sensor to determine whether or not the solvent in the solvent cartridge is consumed when the ink concentration of any one of the circulation tanks is higher than a predetermined range; (h) adjusting the ink concentration of a corresponding one of the circulation tanks by supplying the solvent to the corresponding circulation tank when the solvent remains in the solvent cartridge; and (i) generating a message signaling that the solvent in the solvent cartridge is consumed when the solvent in the solvent cartridge is consumed.
In addition, to achieve the above objective, there is provided an ink delivery system of a liquid-type electrophotographic printer including: circulation tanks for receiving ink to be supplied to respective developing units; concentration sensors each for detecting a concentration of ink in the corresponding circulation tank; ink cartridges which store concentrated ink to be supplied to the respective circulation tanks and are directly connected to the respective circulation tanks; and a solvent cartridge which stores a solvent to be supplied to the circulation tanks and is directly connected to the circulation tanks.